Fast Formula not updating earnings rate

Summary:

Updating the hourly rate through Earnings fast formula only taking new rate

Content (required):

We created an element for supplemental pay (foreman pay) that paid a certain amount until the approved rate change on Jan-01-2023. I updated the fast formula (CPAY Foreman Regular Pay Earnings) to have a start date of Jan-01-2023 and the "l_actual_amount" variable was changed from $1.25 to $3.00, original code in snippet below (it's roughly line 392, if that helps).

The problem is any retro gets paid at the new amount, or more specifically it pays the difference to the new rate. I tried creating a CIR element so I could update the RATE_AMOUNT and it then paid the supplemental pay at the person's full hourly rate, and then the retros would not trigger. In order to get retros to trigger and to not pay at the hourly rate, I end-dated the CIR element which allowed us to get the person paid.